We are looking to make up about 3 portable signs, 4'x8' on a trailer axle that we can move around to various places throughout the season for advertising purposes.

I am wondering what sort of lighting effect we could do that would be able to last 6-8 hours from a deep cycle battery since many of the places we will want to use these will not have an electrical hookup handy.

How long will the automotive neon tubes run from a 12 volt source before draining the battery? What about the new style LED christmas light strings?

If you can, design your 4 by 8 sign with some cut out portions to help eliminate the ability to catch the wind, thereby getting blown over.
Of course these cut out areas could also help to create sort of a "3-D" look to the signs.
My 4 by 8 sign on my homemade axle blew over so many times!
I finally have enough 5 gallon buckets full of concrete chained and wired to the sign to keep it under control.
I think it took about five buckets and cutting the "R" out of GRIN to keep it where I wanted it?